Ultra-wideband (UWB) communication systems employ very short pulses of electromagnetic radiation or impulses with short rise and fall times which results in a spectrum with a very wide bandwidth. UWB communications have a number of advantages over conventional systems. The very large bandwidth for instance facilitates very high data rate communications and since pulses of radiation are employed, the average transmit power may be kept low even though the power in each pulse is relatively large. Since the power in each pulse is spread over a large bandwidth the power per unit frequency may be very low, allowing UWB systems to coexist with other spectrum users and providing a low probability of intercept. UWB techniques are attractive for short range wireless devices, such as radio frequency identification (RFID) systems, because they allow devices to exchange information at relatively high data rates. For instance, an Ultra Wideband Radio Frequency Identification Technique system may be seen in the Reunamaki U.S. Pat. No. 7,733,229 in which UWB techniques are applied to RFID in which a reader generates a UWB IR interrogation signal and receives a UWB IR reply signal from an RFID tag in response to the interrogation signal.
Federal Communications Commission (FCC) defines a UWB pulse as one whose 10 dB bandwidth either is at least 500 MHz or whose fractional bandwidth is greater than 0.20. The 500 MHz minimum bandwidth limit sets a threshold at 2.5 GHz. Below this 2.5 GHz threshold signals are considered UWB if their fractional bandwidth exceeds 0.20, while above the threshold signals are UWB if their bandwidth exceeds 500 MHz. Fractional bandwidth is defined as the ratio of the 10 dB bandwidth to the center frequency. For example, a 500 MHz 10 dB bandwidth UWB signal centered at 6 GHz has a fractional bandwidth of 0.083 (500/6000). For UWB whose center frequency is greater than 2.5 GHz, the 500 MHz 10 dB analog bandwidth needs to be processed.
In our past U.S. Pat. No. 8,627,971, dated Jan. 14, 2014 for a Pulse-Level Interleaving for UWB Systems, a UWB transmitter transmits a multi-pulse per bit signal to a UWB receiver for multi-bit processing. A bit stream is transmitted using a plurality of UWB pulses for each bit frame. The pulse level interleaving of the pulses is accomplished prior to transmission of the signals by a plurality of UWB transmitters operating at the same time. The receiver de-interleaves the pulses and then aggregates the energy from the multiple pulses within each frame.
Other prior art patents and publications may be seen in the Dallum et al. U.S. Patent Application Publication No. 2010/0232472 for a UWB receiver which receives from a transmitter two identical impulses or RF burst packets that are spaced a fixed interval apart. An analog circuit amplifies both signals and sends them through two different paths. One path is non-delayed and the other path delays the incoming signal. The analog circuit's output signal is then digitized to produce a digital output. The front-end of this receiver is a standard architecture for a Super Heterodyne receiver. Dallum's invention transforms RF to digital by feeding a self-mixed output (multiplier output) to a comparator circuit which then produces a digital output. Dallum has a fixed receiver architecture.
The Thibault U.S. Patent Publication No. 2011/0163788 receives and duplicates an input signal and delays one of the signals relative to the other by the output pulse duration and combines the pulses to generate an output pulse of smaller duration than the input pulse duration. Thibault is adding two pulses of a finite duration together in an effort to create an output pulse that is of an even smaller duration. He is trying to create a short pulse from two larger pulses.
The Choi U.S. Patent Publication No. 2004/0223556 is a method for transferring and receiving ultra wideband signals using a differential phase shift keying scheme. The UWB transmitter includes a differential phase shift keying conversion unit for converting a first bitstream by differential phase shift keying into a second bitstream and a modulation unit for generating a UWB wavelet series based on the second bitstream.
The Chen et al. U.S. Patent Publication No. 2008/0130691 is for a Microsoft Windows BDA digital signal processing system and for a method that can process a non-transport stream. A plurality of analog data packets are received for processing both transport and non-transport signal streams. A splitter receives and duplicates the digital stream to output a first signal stream and a second digital stream. When the second digital stream is a non-transport stream, the non-transport stream controller can transmit it to a storage device, demultiplex and transmit it to a conversion filter. Chen is about broadcast driver architecture (BDA) for digital TV tuning devices. It does not correlate the packets and does not multiply and sum over finite duration any pulses.
None of these prior references mentions a rate conversion and none are summing of correlated pulses. None of the references use multiple pulses (greater than 2) per bit and all possible unique combinations of correlations of pulses mentioned.
The Baker U.S. Patent Publication No. 2005/0078735, unlike the present invention, is for a UWB receiver having a predetermined sequence of pulses stored in memory that is used as a template. The receiver correlates this sequence of pulses with that of the incoming signal much like a RAKE receiver. The sequence of pulses used as a template may be a UWB signal which was captured earlier.
The Piesinger U.S. Patent Publication No. 2010/0253565 is for a TCAS receiver having an antenna to receive an analog signal and an analog to digital converter to convert the analog signal to a digital signal and a field programable gate array using matched filters to match the digital signal to a message to increase the ADS-B squitter sensitivity.
In the present invention the received signals are first processed in an analog circuit and then everything is done digitally over a finite group of samples. The circuit converts the transmitted analog data stream into a digital signal and a digital rate conversion is performed in the process of correlation by the field programmable gate array. The correlation is done with two or more continuous signal streams in which the digital rate conversion is performed in the process of correlation.
The purpose of the present invention is to improve an Ultra Wideband (UWB) digital receiver's performance sensitivity. A key measurement to evaluate a UWB digital receiver's performance sensitivity is Signal to Noise and Distortion Ratio (SINAD). In a communications link, the transmitted signal is degraded by undesired impairments and extraneous signals. The received signal is a superposition of linear additive noise components and nonlinear distortions. Nonlinear distortion comes from a variety of causes, including but not limited to multipath, which not only can distort but also attenuate signals through the different radio frequency phenomena: scattering, reflection, and diffraction. Signal degradation of all these channel impairments result in limiting the potential range of the communications system.
The present invention takes a digitized IF signal output from the ADC which has a finite number of pulses per bit, correlates the pulses and sums the energy of finite duration while reducing the sample rate and then produces all possible combinations of unique correlations of those pulses and finally sums every correlation output together for a cumulative peak detection for severely improved processing gain. The digital signal stream is processed in multiple groups for a multiple pulse per bit varying time delayed correlation.